冰雹形成过程及人工防雹研究综述

Review of advances in hail formation process and hail suppression research

  • 摘要: 冰雹作为一种短时强灾害天气,常给农业、建筑、电力、交通甚至生命财产等造成严重影响,人工防雹也因此受到人们的广泛关注。文中首先介绍了冰雹形成机理和雹云物理研究情况,然后围绕人工防雹机理、技术、科学试验及效果评估这4个方面的研究进行了评述,旨在从理论和实践上总结人工防雹工作的进展,增进对人工防雹科学问题的认知,从而为促进中国人工防雹理论研究和技术进步提供借鉴。研究表明:(1)“累积带理论”和“循环增长理论”是冰雹形成的最常见理论,限于早期的雷达观测技术和缺乏完整的冰雹数值模式,早期认知的冰雹形成机理存在一定的局限。(2)雹胚一般分为冻滴胚和霰胚,冻滴胚由过冷雨滴冻结而成,霰胚则是冰晶、雪花撞冻生长而成。冰雹云中哪种雹胚占优势,主要看云底温度的高低。雹云的发展依赖于水汽条件、动力不稳定条件、风垂直切变等关键因子。(3)人工防雹主要遵循“播撒防雹”和“爆炸防雹”2条技术路线,“利益竞争”和“早期降雨”是常见的6种防雹原理假说中最广泛被用来作为防雹作业设计依据的2种播撒防雹理论。(4)人工防雹技术上多采用通过飞机、地面火箭、地面燃烧炉等向云中播撒人工冰核,或通过地面高炮向云中发射含人工冰核的炮弹等方式,影响冰雹的生长过程从而达到抑制或削弱冰雹生长的目的。(5)大量外场试验证明人工防雹效果有较大的地域差异,需根据各地冰雹云特征及其降雹特点制定和发展本地适用的人工防雹技术体系。(6)人工防雹效果检验仍然是制约人工防雹技术发展的一个“瓶颈”,目前常用的统计检验、物理检验和数值模拟检验技术方法均需要进一步改进和完善。由于雹云变化迅速、降雹过程短促,人工防雹技术实施的时效性以及防雹效果评估仍存在较大的困难。今后应更多地借助多种探测设备进行冰雹云的精细化探测,开展有科学设计的人工防雹外场综合试验,运用统计检验、物理检验和数值模拟相结合的综合检验技术方法评估防雹效果,推动人工防雹事业进一步快速发展。

     

    Abstract: As a kind of short-period severe weather disaster, hails often have severe impacts on agriculture, construction, electricity, transportation and even lives and properties, etc. Therefore, hail suppression is widely concerned worldwide. This paper provides a detailed review of research progress in hail formation mechanism and hail cloud physics from perspectives of mechanism, technology, scientific experiments and effect evaluation of hail suppression for the purpose to gain in-depth knowledge of domestic and international development of hail suppression in both theoretical and practical fields, improve our understanding of scientific problems in hail suppression, and provide references for promoting theoretical research and technological progress of hail suppression in China. Major results as follows: (1) The "theory of zone of accumulation" and the "theory of cyclic growth" are the most common theories of hail formation. Limited by the early radar observation technology and the lack of complete numerical models for hail simulation, the early knowledge of the hail formation mechanism has certain limitations. (2) Hail embryos are generally divided into frozen drop embryos and graupel embryos. Frozen drop embryos are formed by the freezing of supercooled raindrops while graupel embryos are formed by the growth of collision and freezing of ice crystals and snowflakes. What type of hail embryo is dominant in the hail cloud mainly depends on temperature of the cloud base. The development of hail clouds depends on key factors such as water vapor condition, dynamic instability condition, and vertical wind shear, etc. (3) The mechanism of hail suppression mainly follows two technical lines, "hail suppression by seeding" and "hail suppression by explosion". "Competing interests" and "early rainfall" are the two most widely used theories of seeding among the six common hypotheses of hail suppression on which hail suppression operations are designed. (4) Technically, the hail suppression operations mainly include seeding hail clouds with artificial ice nuclei by aircraft, rocket launcher, ground generator, etc., or launching shells with artificial ice nuclei by ground artillery, which can affect the growing process of hail to suppress or weaken the growth of hail. (5) A large number of field experiments of hail suppression have proved that there are regional differences in operation effect of hail suppression. It is necessary to formulate and develop regional hail suppression technology systems adapted to local conditions according to the characteristics of hail clouds and hailstorms in different regions. (6) Evaluating the effect of hail suppression is still a bottleneck problem that limits the development of hail suppression technology. The methods commonly used to assess the effect of hail suppression mainly include statistical, physical, and numerical simulation evaluations, which need further improvement. Due to the rapid changes in hail clouds and short hailstorm processes, there exits great difficulties in the timeliness of implementation of hail suppression operation and the effect evaluation of hail suppression. It will start from carrying out fine detection of hail clouds based on a variety of observation equipment and comprehensive field experiments of hail suppression with scientific design. Statistical, physical and numerical simulation approaches should be combined to evaluate the effect of hail suppression and promote further development of hail suppression technology in future.

     

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